Typically, methods of forming TCOs on glass substrates require high glass substrate temperatures. Such methods include chemical pyrolysis where precursors are sprayed onto the glass substrate at approximately 400 to 500 degrees C., and vacuum deposition where the glass substrate is kept at about 150 to 300 degrees C. Unfortunately, TCO films such as SnO2:F (fluorine doped tin oxide) formed on glass substrates by chemical pyrolysis suffer from non-uniformity and thus may be unpredictable and/or inconsistent with respect to certain optical and/or electrical properties.
Sputter deposition of a TCO (transparent conductive oxide) at approximately room temperature would be desirable, given that most float glass manufacturing platforms are not equipped with in-situ heating systems. An additional potential advantage of sputter-deposited TCO films is that they may include the integration of anti-reflection coatings, resistivity reduction, and so forth.
There is often a need to thermally temper coated articles having a glass substrate coated with a TCO film/coating. For instance, in certain applications tempering is required by code (e.g., for windows over doorways, for windows identified as breakable windows for firemen, and other applications). Thermal tempering typically requires heating the glass substrate with a coating thereon in a tempering furnace at a temperature of at least about 580 degrees C., more preferably at least about 600 degrees C., and often at least about 620 or 640 degrees C. (e.g., for at least about 2 minutes, more preferably for at least about 5 minutes). Thus, it will be appreciated that thermal tempering involves very high temperatures.
Unfortunately, it has been found that glass substrates supporting sputter-deposited TCOs cannot be thermally tempered without the TCOs suffering a significant loss in electrical conductivity. Glass tempering temperatures (see above) of typical sputter-deposited films causes a rapid conductivity drop in certain TCOs (e.g., sputter-deposited zinc oxide inclusive TCOs).
Thus, it will be appreciated that there exists a need in the art for an improved technique or method of tempering glass substrates including a film/coating thereon that can result in an effective and/or efficient tempered glass substrate with a TCO film thereon.
In certain example embodiments of this invention, a method is provided for making a thermally tempered coated article including a tempered glass substrate with a TCO film thereon. Initially, an amorphous metal oxide film is sputter-deposited onto a non-tempered glass substrate, either directly or indirectly. In certain example embodiments, the sputter-deposited amorphous metal oxide film may be of or include an oxide of Sn and/or Sb (e.g., SnOx:Sb). As sputter-deposited, the metal oxide film is rather high with respect to visible light absorption, has a high sheet resistance (i.e., not truly conductive), and is amorphous. The glass substrate with the amorphous film thereon is then thermally tempered. The thermal tempering typically involves heating the glass substrate with the amorphous film thereon in a tempering furnace at a temperature of at least about 580 degrees C., more preferably at least about 600 degrees C., and often at least about 620 or 640 degrees C. The glass substrate with the film thereon may be in the tempering furnace for at least about 2 minutes, more preferably for at least about 5 minutes, in certain example embodiments of this invention. The thermal tempering causes the amorphous non-conductive film to be transformed into a crystalline transparent conductive oxide (TCO) film. In other words, the heat used in the thermal tempering of the glass substrate causes the amorphous film to turn into a crystalline film, causes the visible transmission of the film to increase, and causes the film to become electrically conductive. In short, the thermal tempering activates the film.
In certain example embodiments of this invention, the amorphous film prior to tempering and the crystalline TCO following tempering may be of or include SnOx:Sb (x may be from about 0.5 to 2, more preferably from about 1 to 2, and sometimes from about 1 to 1.95). The film may be oxygen deficient (substoichiometric in certain instances). The Sn and Sb may be co-sputtered in an oxygen inclusive atmosphere (e.g., a mixture of oxygen and argon) to form the film in certain example embodiments of this invention, with the Sb being provided to increase conductivity of the crystalline film following tempering. In certain example embodiments, the Sb is provided for doping purposes, and can make up from about 0.001 to 30% (weight %) of the amorphous and/or crystalline metal oxide film (from preferably from about 1 to 15%, with an example being about 8%). If the Sb content is higher than this, the lattice is disturbed too much and mobility of electrons is also disturbed thereby hurting conductivity of the film, whereas if less than this amount of Sb is provided then the conductivity is not as good in the crystalline film.
In certain example embodiments of this invention, there is provided a method of making a thermally tempered coated article including a transparent conductive film on a tempered glass substrate, the method comprising: providing a glass substrate; sputter-depositing an amorphous film comprising Sn and Sb on the glass substrate; thermally tempering the glass substrate with the amorphous film comprising Sn and Sb thereon; and wherein heat used in said tempering causes the amorphous film to transform into a crystalline film, and wherein the crystalline film is transparent to visible light and electrically conductive.
In other example embodiments of this invention, there is provided a method of making a thermally tempered coated article including a transparent conductive film on a tempered glass substrate, the method comprising: providing a glass substrate; sputter-depositing an amorphous film on the glass substrate; thermally tempering the glass substrate with the amorphous film thereon; and wherein heat used in said tempering causes the amorphous film to transform into a crystalline film, and wherein the crystalline film is transparent to visible light and electrically conductive.
In still further example embodiments of this invention, there is provided a coated article comprising: a thermally tempered glass substrate; and a crystalline transparent conductive film comprising a metal oxide supported by at least the tempered glass substrate, and wherein the transparent conductive film comprises Sn and Sb, and has an Sb content of from about 0.001 to 30%.